Cancer risk in persons with new-onset anaemia: a population-based cohort study in Denmark

Background

The time interval from first symptom and sign until a cancer diagnosis significantly affects the prognosis. Therefore, recognising and acting on signs of cancer, such as anaemia, is essential. Evidence is sparse on the overall risk of cancer and the risk of specific cancer types in persons with new-onset anaemia detected in an unselected general practice population. We aimed to assess the risk of cancer in persons with new-onset anaemia detected in general practice, both overall and for selected cancer types.

Methods

This observational population-based cohort study used individually linked electronic data from laboratory information systems and nationwide healthcare registries in Denmark. We included persons aged 40–90 years without a prior history of cancer and with new-onset anaemia (no anaemia during the previous 15 months) detected in general practice in 2014–2018. We measured the incidence proportion and standardised incidence ratios of a new cancer diagnosis (all cancers except for non-melanoma skin cancers) during 12 months follow-up.

Results

A total of 48,925 persons (median [interquartile interval] age, 69 [55–78] years; 55.5% men) were included in the study. In total, 7.9% (95% confidence interval (CI): 7.6 to 8.2) of men and 5.2% (CI: 4.9 to 5.5) of women were diagnosed with cancer during 12 months. Across selected anaemia types, the highest cancer incidence proportion was seen in women with ‘anaemia of inflammation’ (15.3%, CI: 13.1 to 17.5) (ferritin > 100 ng/mL and increased C-reactive protein (CRP)) and in men with ‘combined inflammatory iron deficiency anaemia’ (19.3%, CI: 14.5 to 24.1) (ferritin < 100 ng/mL and increased CRP). For these two anaemia types, the cancer incidence across cancer types was 10- to 30-fold higher compared to the general population.

Conclusions

Persons with new-onset anaemia detected in general practice have a high cancer risk; and markedly high for ‘combined inflammatory iron deficiency anaemia’ and ‘anaemia of inflammation’. Anaemia is a sign of cancer that calls for increased awareness and action. There is a need for research on how to improve the initial pathway for new-onset anaemia in general practice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09912-7.

Diagnostic workup of cancer in patients with new-onset anaemia: a Danish cohort study in general practice

BACKGROUND

Anaemia is associated with adverse outcomes, including increased morbidity and all-cause mortality. Diagnostic workup of patients with anaemia is essential to detect underlying disease, especially undiagnosed malignancy.

OBJECTIVE

To describe the cancer-relevant diagnostic workup in patients with new-onset anaemia detected in general practice. An additional aim was to analyse associations between patient characteristics and the diagnostic workup.

DESIGN

Observational population-based cohort study using electronic laboratory and register data.

SETTING

Danish general practice.

SUBJECTS

Patients aged 40-90 years with new-onset anaemia (no anaemia in the preceding 15 months) detected in general practice. Patients were identified in Danish laboratory information systems and nationwide registries in 2014-2018.

MAIN OUTCOME MEASURES

We measured the proportion of patients receiving predefined diagnostic investigations, that is, cancer patient pathway, colonoscopy, gastroscopy, computerised tomography (CT) scan, faecal test for haemoglobin, and bone marrow examination within three months of the anaemia index date.

RESULTS

We included 59,993 patients, and around half of the patients with 'iron deficiency anaemia', 'anaemia of inflammation', or 'combined inflammatory iron deficiency anaemia' had no cancer-relevant diagnostic investigations performed. Patients aged 60-79 years and patients with severe anaemia were more likely to have investigations performed, while patients with comorbidity were less likely to have investigations performed.

CONCLUSION

Around half of the patients with anaemia subtypes that may indicate underlying cancer had no cancer-relevant diagnostic investigations performed. This may represent missed diagnostic opportunities. Future interventions are needed to improve the diagnostic workup of cancer in patients with anaemia, for example, laboratory alert systems and clinical decision support.KEY POINTSThe general practitioners are often the first to detect anaemia and its underlying disease (e.g. undiagnosed malignancy).Large-scale studies are needed on the diagnostic workup of patients with anaemia in general practice in relation to an underlying malignancy.This study shows that the majority of patients with anaemia had no cancer-relevant diagnostic investigations performed, which may cause diagnostic delay.Interventions seems needed to improve the diagnostic workup of cancer in these patients to ensure timely diagnosis.

Insufficient classification of anaemia in general practice: a Danish register-based observational study

BACKGROUND

Anaemia can be a pointer of underlying severe disease, including undiagnosed malignancy. Subsequent blood tests are essential to classify the anaemia into subtypes and to facilitate targeted diagnostic investigation to ensure timely diagnosis of underlying disease.

OBJECTIVE

We aimed to describe and classify anaemia based on laboratory tests from patients with new-onset anaemia detected in general practice. An additional aim was to analyse associations between patient characteristics and unclassified anaemia (not classifiable according to an algorithm).

DESIGN

Population-based cross-sectional study.

SETTING

Danish general practice.

SUBJECTS

A total of 62,731 patients (age: 40-90 years) with new-onset anaemia were identified in Danish laboratory information systems and nationwide registries, and data were obtained for 2014-2018.

MAIN OUTCOME MEASURES

We measured the proportion of patients classified into subtypes of anaemia based on blood tests requested by general practitioners within 31 days of the anaemia index date.

RESULTS

Of the 62,731 patients with new-onset anaemia, we identified unclassified anaemia in 78.9% (95% confidence interval (CI): 77.3-80.5) of men and 65.1% (CI: 63.4-66.9) of women. The likelihood of unclassified anaemia increased with age, increasing comorbidity and decreasing severity of anaemia.

CONCLUSION

The majority of patients with new-onset anaemia could not be classified through a simple algorithm due to missing blood tests, which highlights a potential missed opportunity for diagnosis. Standardised laboratory testing of patients with anaemia is warranted to ensure adequate follow-up and early detection of underlying severe disease.KEY POINTSAnaemia can be a sign of malignancy, and anaemia classification is an important step in the diagnosis of underlying disorders.The majority of patients with anaemia could not be classified according to a simple algorithm due to missing blood tests.Some patient characteristics were associated with a high risk of unclassified anaemia: high age, high comorbidity, and severe anaemia.Standardised laboratory testing in patients with anaemia is needed to inform targeted diagnostic investigation to ensure timely diagnosis.